This invention pertains to means of rapidly and reliably attaching a small electric motor to its mounting surface. More specifically, this invention relates to means for attaching a motor to a support surface without the use of screws or other loose hardware.
Small electric motors, typically those having an outside diameter of less than three inches, are used in a myriad of consumer, industrial, and medical devices such as computer printers, ticket printers, centrifuges, and the like. In almost all cases, such motors are used to provide rotary motion to these devices and are attached to a mounting surface or plate with the motor shaft, or drive shaft, protruding through the plate. Pulleys, spur gears, couplings, shafts, or the like may be attached to the drive shaft and form the beginning of the device drive train.
Almost universally, such small motors are secured to the mounting plate by two to four screws which pass through the plate from the drive shaft side (hereinafter xe2x80x9cfront sidexe2x80x9d) and engage threaded holes in the motor face or endbell. During the assembly of the motor to the device, the loose mounting screws are oriented, inserted through the mounting plate, and then driven into the motor face endbell with relative ease due to the fact that other components that form the drive train are typically installed after the drive motor is installed.
Reversing the procedure, however, is much more difficult. When a motorized device fails, in many cases it is the motor that fails due to brush failure, overheating, shorted windings, and the like. Typically it is only the motor that needs to be replaced to put the unit back into service. However, since the motor is secured to the mounting plate by screws that engage the motor from the front side, access to that side must be provided and that often requires disassembly of the drive train. This can be a time-consuming process involving costly labor to disassemble the device, replace the motor, and reassemble the unit. In fact, such service costs can be so significant that the entire device is replaced rather than merely replacing the motor.
Thus, there is a need in the art for a motor mounting system which overcomes the above disadvantages by providing means to install and, if need be, to replace the motor from the back side or motor side of the mounting plate. In addition, there is a need for a mounting device that allows the rapid installation of a motor on an assembly line by eliminating the need for loose attaching screws.
In order to meet the needs in the art described above, the present motor mount system has been devised. The invention consists of a plastic, molded motor endbell having two integral resilient lever arms that engage mating holes in the mounting surface. Each lever arm is in the form of a curved leaf spring which extends rearward along the sides of the motor housing. The integral lever arms are free to swing away from the sides of the housing by a diminished portion of their structure adjacent the endbell which forms a xe2x80x9cliving hinge.xe2x80x9d The mounting plate or support surface to which the motor is to be mounted is provided with three holes, one for receiving a locating boss of the motor endbell which is part of the motor housing, and two mounting holes for receiving the ends of the lever arms. All three holes are in line with the center hole and ultimately with the motor drive shaft. The center hole is sized to receive an alignment boss which projects from the endbell and so that a spur gear typically affixed to the drive shaft may pass through the hole.
Mounting the motor is accomplished as follows. First, the motor is presented to the mounting surface and the boss of the motor endbell is inserted into the center hole. Next, the lever arms are flexed outward and a foot at the front end of each lever is inserted through the mounting holes. The lever arms are then squeezed inwardly and their motion causes their ends (hereinafter xe2x80x9cfeetxe2x80x9d) to lever-lock against the opposite side of the mounting surface. As greater force is applied, the naturally bowed lever arms straighten against the applied force and lengthen sufficiently so that slots in the arms clear bent-out tabs of the motor housing and move to a position behind the tabs. Thereafter, a release of pressure on the arms causes them to shorten and resume their natural bowed shape placing them behind the tabs and locking them into place. Because this final locking function occurs without lever rotation, the feet of the lever arms remain clamped into the mounting surface. Thus, by these mechanical relations, the motor housing becomes securely affixed to the mounting surface until it is later released by unlocking the lever arms and reversing the installation process.
More specifically, the applicant has invented an electric motor with integral attachment means comprising a motor housing, at least two lever arms spaced equally about the circumference of the motor housing and hingeably connected to the motor housing at living hinge joints, the levers being movable between clamped and released positions, and an attachment foot located at one end of each lever arm being integral therewith, the foot lying adjacent the hinge joint and extending radially outwardly from the motor housing to a distal end thereof. The lever arm further includes a radially inwardly-projecting heel which occupies a notch in the motor housing when the lever arm is in the clamped position. The lever arms are resilient and radially outwardly bowed in their relaxed state and further include a slot adjacent a second end thereof, the slot being engageable with a motor housing locking tab when in the clamped position. The locking tab extends radially outward from the motor housing. The housing includes an endbell at a mounting end thereof and the feet of the attachment levers extend axially beyond the endbell. The motor housing includes a mounting plate with a center hole for receiving an axially projecting boss on the endbell and two mounting holes located on opposite sides of the center hole laterally, each mounting hole having sidewalls forceably engaging a lever arm foot. The mounting holes have axes which are parallel to the motor housing axis. The mounting holes also have radially divergent sidewalls in the axial direction away from the housing. The endbell, hinges, and lever arms of the motor housing may be portions of a unitary molded plastic structure. The hinge joint of the motor housing provides a laterally deflectable interconnection of the arms with the housing, while the foot of each lever arm provides a resiliently-loaded clamp force against the housing and the mounting plate.
It is therefore the primary object of the invention to provide a self-contained mounting device as an integral part of an electric motor which allows the easy installation of the motor and eliminates the need for loose hardware. It is a further object of the invention to accomplish this primary object with cooperating mounting surface structures which may be economically formed. These and other objects and advantages of the present invention will be apparent to those of skill in the art from the following drawings and description of the preferred embodiment.